The present invention relates to a method of preparing a dry animal feed with a predetermined water content. According to the method, there is added to a dry animal feed mixture an emulsion of water emulsified in a hydrophobic component with a melting point of at least 15xc2x0 C., suitably at least 20xc2x0 C., in such an amount that the animal feed obtains the predetermined water content.
In the breeding of animals, it is of economic importance that the animals obtain feed which does not only contain correctly adapted nutritive substances but is also given in correct amounts, thereby maximising the growth per kilogram of consumed feed. However, it has been found difficult in the administration of dry animal feed to calculate the active content in the animal feed owing to a varying water content. Variations in the water content of more than 2% from the desired value are not unusual. When breeding mink and fox it is also important that the dry animal feed mixtures contain a considerable amount of water, thereby reducing the risk of dehydration in cold weather. There are several reasons why the water content in dry animal feed varies. One reason is that the water contents in the ingredients included, for instance corn, vary from time to time. Another reason is that when grinding the ingredients included, when mixing the various ingredients and in optional pelletizing, extrusion and/or expansion, heat is supplied, which results in evaporation of water. Also in storage, considerable amounts of water may evaporate.
It has also been found that direct addition of water to the animal feed mixture in many cases causes difficult problems, such as caking, above all of pulverulent animal feed, and mould. The object of the present invention therefore is to provide a method of preparing a dry pulverulent animal feed with small or insignificant variations in the water content, while at the same time caking of the animal feed and mould are reduced or prevented.
The present invention generally relates to a method of preparing a ground dry animal feed with a predetermined increased water content. The present method comprises adding to the animal feed an emulsion containing water emulsified in a liquid hydrophobic component comprising a lipid, a fatty acid or a mixture thereof and having a melting point of at least 15xc2x0 C., measured according to ASTM 15-04 No. D5440, in such an amount that the prepared animal feed obtains the predetermined water content, mixing the emulsion with the animal feed, and, if necessary, cooling the prepared animal feed to a temperature below the melting point of the hydrophobic component.
It has now surprisingly been found that a ground dry animal feed with a predetermined increased water content can be prepared by the steps of adding to the animal feed an emulsion containing water emulsified in a liquid hydrophobic component, comprising a lipid, a fatty acid or a mixture thereof and having a melting point of at least 15xc2x0 C., suitably at least 20xc2x0 C., measured according to ASTM 15-04 No. D5440, in such an amount that the prepared animal feed obtains the predetermined water content, mixing the emulsion with the animal feed, and, if necessary, cooling the prepared animal feed to a temperature below the melting point of the hydrophobic component. The inventive method results in a dry animal feed, whose water content varies to a smaller extent than an animal feed prepared in a conventional manner. According to the method, the animal feed mixture is also hydrophobated, which results in reduced tendency to form lumps or to mould. The inventive method can be applied to all types of dry animal feed mixtures, such as fine-grained, pelletized, extruded or expanded dry animal feed mixtures. The amount of the hydrophobic component suitably is 1-8 parts by weight per part by weight of water. To obtain a stable emulsion, also an emulsifier is usually added in an amount of 0.005-0.05 parts by weight per part by weight of hydrophobic component.
The emulsion can be added at any time after grinding of the components included, either to a ground component or to the dry animal feed mixture before pelletizing, extruding or expanding, or after pelletizing, extruding or expanding, or by a combination of the stated points of addition.
In the preparation of a conventional dry animal feed, 0.5-4% by weight of water, based on the final weight of the dry animal feed, is normally lost. In the method according to the invention, 1-10% by weight, based on the final weight of the dry animal feed, of an emulsion is usually added in order to at least partly compensate for the amount of water lost in the preparation of animal feed. The ratio of water to hydrophobic component varies according to the solidifying point of the component. The higher solidifying point the more water can be used in relation to the hydrophobic component. The weight ratio of water to hydrophobic component preferably is 1:1-1:2 and the amount of water in the emulsion is 1-4%, based on the final weight of the dry animal feed. The emulsifier content based on the amount of hydrophobic component preferably is between 1 and 4% by weight. Even if hydrophobic components with a melting point of 15xc2x0 C. can be used, hydrophobic components with a melting point of 30xc2x0 C. min are preferred. Examples of suitable hydrophobic components are fats, such as lard, tallow, chicken grease, bone grease, slaughtering grease, cured vegetable oils and cured fish oil; fatty acids and distillation residues of fatty acids containing mono-, di- or triglycerides. Normally the melting point is lower than 90xc2x0 C.
The emulsifiers are conventional emulsifiers for hydrophobic, water-soluble products. In the first place, use is made of nonionic surfactants, which contain an aliphatic hydrocarbon group having 8-24 carbon atoms, preferably 12-22 carbon atoms. The nonionic surfactants suitably consist of nonionic polyethylene glycols, such as ethoxylate of carboxylic acids, ethoxylate of mono-, di- or triglycerides, ethoxylate of mono-, di- or triesters of sorbitan or ethoxylate of fatty alcohols. Other suitable nonionic surfactants are mono-, di- or triglycerides based on fatty acids having 12-22 carbon atoms, or mono-, di- or triesters of sorbitan based on fatty acids having 12-22 carbon atoms. Of the described nonionic surfactants, those having an HLB value of 2-12, preferably 2-9, and most preferred 3-7 are particularly suitable. The stated HLB values are determined in consideration of the weight percentage of hydrophilic groups according to the equation
HLB=WA+WE/5
wherein WA is the weight percentage of polyalcohol, such as glycerol o r sorbitol, in % of the weight of the surfactant and WE is the weight percentage of polyethylene oxide in % of the weight of the surfactant.
Especially preferred nonionic surfactants are castor oil ethoxylate, ethoxylated sorbitan oleate and sorbitan esters.
In addition to nonionic surfactants containing an aliphatic hydrocarbon group having 8-24 carbon atoms, also phosphatides, such as lecithin and cephalin, have excellent properties. Preferred phosphatides are lecithin and acetylated lecithin.
The preparation of dry animal feed begins by grounding many of the raw products, such as cereals. This causes losses of water. Then the dry ingredients are mixed. Some lipids, suitably in liquid phase, and fatty acids can also be added and admixed to the dry animal feed. Then there are a few different modes of treatment. For instance, the mixed dry animal feed can be packaged directly. Another possibility is thermal treatment of the dry animal feed in a pelletizing machine at 55-90xc2x0 C., in an expander at 90-120xc2x0 C. or in an extruder at 130-160xc2x0 C. or by a combination of these thermal treatments before packaging. Water evaporates in the treatments at elevated temperatures. The higher treatment temperature and the longer treatment time, the more water evaporates.
According to the invention, water and an emulsifier can be added to the emulsion in one or more steps to increase the water content of the dry animal feed to the desired level. The addition can be made
a) to one of the ground components or to the dry animal feed before a possible treatment at an increased temperature,
b) after one or more treatments of the animal feed at an increased temperature, or
c) by a combination of the points of addition according to a) and b).
After adding, the emulsion is mixed in the animal feed, and if the hydrophobic component has a low melting point, the animal feed mixture is cooled to a temperature below the melting point of the hydrophobic component. With a view to obtaining a granule-like powder of good quality and stability, it is suitable to pelletize the animal feed in a finalising treatment at an increased temperature. The pelletizing operation can possibly be followed by crushing of the pellets to the desired particle size.
The present invention is further illustrated by the following nonlimiting Examples.